Blood vessel occlusions are commonly treated by mechanically enhancing blood flow in the affected vessels, such as by employing a stent. Stents are used not only for mechanical intervention but also as vehicles for providing biological therapy. To effect a controlled delivery of an active agent in stent medication, the stent can be coated with a biocompatible polymeric coating. The biocompatible polymeric coating can function either as a permeable layer or a carrier to allow a controlled delivery of the agent.
Although stents work well mechanically, the chronic issues of restenosis and, to a lesser extent, stent thrombosis remain. Pharmacological therapy in the form of a drug delivery stent appears to be a feasible means to tackle these issues. Polymeric coatings placed onto the stent serve to act both as the drug reservoir and to control the release of the drug. One of the commercially available polymer coated products is stents manufactured by Boston Scientific. For example, U.S. Pat. Nos. 5,869,127; 6,099,563; 6,179,817; and 6,197,051, assigned to Boston Scientific Corporation, describe various compositions for coating medical devices. These compositions provide to stents described therein an enhanced biocompatibility and may optionally include a bioactive agent. U.S. Pat. No. 6,231,590 to Scimed Life Systems, Inc., describes a coating composition, which includes a bioactive agent, a collagenous material, or a collagenous coating optionally containing or coated with other bioactive agents.
There are a very large number of biodegradable polymers for coating a stent. Aliphatic polyesters represent a particularly important example, as their biocompatible and biodegradable (resorbable) properties make them attractive for a host of applications including drug delivery vehicles, tissue engineering scaffolds, implant materials, stents and stent coatings. Commercially available aliphatic polyesters such as poly(ε-caprolatone) (PCL), polylactide (PLA), and polylactide-co-glycolide (PLGA) have proven useful in many of these applications. However, these conventional polyesters do not possess functionality. The ways to functionalize these polymers outside of the backbone ester structure are limited. As a result, the application of these polymers is limited only to applications that can be satisfied by their inherent structure.
Therefore, there is a need for polymeric materials which can be tailored to meet need of a coating on a medical device.
The polymer and methods of making the polymer disclosed herein address the above described problems.